This question relates to the physics of a situation that occurs in Star Wars VII. I am wondering if there has been any canon to address this.

A white dwarf is an object with about the mass of the sun in about the same volume as Earth.

Starkiller base is a planet (presumably Earth sized) that

pulls a sun-like star inside it to provide power for its weapon.

If gravitational and quantum physics are at all similar in a galaxy far, far away as in our own galaxy, then to me it seems like Starkiller base would fulfill the conditions of becoming a white dwarf. At the very least, the gravity at the surface of the planet would become super strong and nothing -- buildings, people, mountains, trees -- would be able to remain standing.

How does Starkiller base keep from turning into a white dwarf, and how does it survive the awesome increase in surface gravity?

This answer indicates that it draws away the sun's "dark energy". Presumably that still leaves enough mass to prevent the star from immediately going nova.
– ValorumApr 5 '16 at 21:21

Don't forget that some kind of gravity control exist in the Star Wars universe, as evidenced by no one being weightless when traveling through space.
– HypnosiflApr 5 '16 at 22:08

My interpretation is that Starkiller Base sucks only a relatively small amount of energy out of its sun, and only from the outer layers, which is why the sun goes dark. Still a huge energy source on the human scale of things, but not enough to significantly affect gravity.
– Harry JohnstonApr 6 '16 at 2:38

@HarryJohnston, there's energy all throughout the star, and in fact the energy density and temperature get higher the further in to the star you go. Pulling off the outer layers of a star would make it brighter, not dimmer.
– NeutronStarApr 6 '16 at 14:25

@Joshua: if you actually took the outer layers away, then yes. If you just suck out all the heat, they'll go dark. (OK, that's thermodynamically impossible, but this is Star Wars physics.)
– Harry JohnstonApr 6 '16 at 21:47

3 Answers
3

The weapon ran on a type of dark energy called "quintessence", which was ubiquitous in the universe, and offered a practically unlimited power source to the First Order. Using a star as a power source, an array of collectors on one side of the planet would gather dark energy in stages, redirecting it to the planetary core, where it was held in place by the natural magnetic field of the planet, as well as an artificial containment field maintained by the machinery the First Order had installed within the crust.

So the star is merely a power source to collect the real energy. In other words, SKB is likely using the fusion materials and process of the star to power the collectors and the containment field.

To your question, a White Dwarf has no usable fuel for its fusion left, and thus collapses in on itself.

The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. As a result, it cannot support itself by the heat generated by fusion against gravitational collapse

It would seem that SKB didn't fully use up all of the fuel of the star. The best explanation as to why it didn't all the fuel is that the thermal oscillator was damaged and subsequently destroyed, thus interrupting the process of using the star as fuel. As such, the uncontrolled solar reaction destroyed SKB and formed a new star. I would expect that the process SKB performed on the star would have greatly shortened its life (since it was well into the process of charging the weapon with dark energy). It would probably decay quickly into a red giant and eventually form a White Dwarf (provided the dark matter that had already been collected didn't interact with the star in some other way).

As to why the gravity didn't change, it's well established that gravity manipulation exists in the Star Wars universe (most notably Interdictor Cruisers, which use large gravity wells to yank ships out of hypperspace, as happened in the Rebels episode Stealth Strike). I would assume the same technology could be scaled up to control the absorption of a star.

Wait, so the star was just the power source for their power source? Why did they need to drain it, then? Wouldn't they just need a little solar energy to jumpstart the quintessence harvesting process, and then use the energy from that to harvest subsequent quintessence?
– user867Apr 6 '16 at 5:50

Stars are powered by dark energy? That makes no sense. The defining characteristic of dark energy is that it is dark, as in cannot be seen by astronomers like, say, starlight.
– J DoeApr 6 '16 at 8:26

@JDoe Nowhere is it (or I) claiming that the stars are powered by dark energy (and the dark energy info came directly from the canon novel for TFA). But if SKB had collected enough dark energy to fire before the process was stopped, who is to say it couldn't interact with a dying star? Remember, a dark energy sub-hyperspace weapon that sucks up stars is fictional anyways.
– MachavityApr 6 '16 at 12:08

@user867 SKB can't really use quintessence as a power source. It needs to contain and convert it, then rupture the containment so it ejects in the direction you want to fire. In that sense, it sounds like lava to us. It's something we understand but, beyond using ditches and fire hoses to steer it, we can't really "use" it.
– MachavityApr 6 '16 at 12:16

@Machavity, how much of the star gets absorbed in the process, and why does it go dark?
– NeutronStarApr 6 '16 at 14:27

Starkiller Base will have to contain all of the energy from a star in
some sort of massive, planet-sized battery. Most of the energy from
the star will go into this energy beam, but not all of it; nothing is
100% efficient after all. Assuming for a second that Starkiller Base
is 99.999 percent efficient at converting the mass of a star into a
system-killing beam, that still means 1.5 x 1027 Joules of
energy emitted as waste heat. That’s the equivalent of 350 quadrillion
tons of TNT, or thirty trillion Little Boy-sized nuclear bombs. ...

But what exactly happens to this waste heat? Since The Force Awakens
doesn’t show any radiators sticking up out of the atmosphere, so all
of this energy must go into the atmosphere. ...

The waste heat from the Starkiller’s stellar mass to energy conversion
is enough to raise the temperature of the atmosphere of the First
Order’s megaweapon to nearly 300 million degrees. This is the problem
with turning matter into energy: you get a lot of energy. If the mass
to energy conversion process of the Starkiller is just the tiniest bit
inefficient, it’s enough to vaporize everything on the surface.

From a (real world) physics point of view, it makes absolutely no sense at all to absorb a star into a planet.

Compared to a star a (rocky) planet has an insignificant mass and volume. Absorbing a star (in the form of its matter) is therefore rather improbable. And even if they found a way to absorb its mass into SKB, they would have the slight problem of gravity.

A star (to be called as such as in having nuclear fusion going on) has a mass of roughly 75 times the mass of Jupiter. If you compress that to a size roughly that of earth, the gravity on the surface would roughly be 10-100 times that of normal earth gravity.

Everyone on SKB would have been pressed flat to the ground and couldn't have moved much anymore.

So absorbing the matter of a star is highly unlikely. On the other hand, energy itself has no mass. So what they could have absorbed actually was the stars energy and stored that in SKB.

If it were possible to absorb a stars energy the right way, it would even fit to what was depicted in the movie. A star is gas in a hydrostatic equilibrium, meaning it is compressed by its gravitational pressure and the fusion power released counteracts that contraction. If you'd absorb both energies (fusion energy and gravitational energy) you'd for once have a HUGE energy source and the star's matter would slowly dim and become a rather compact, heavy and small dark object, that couldn't be seen any more other than with specialized equipment.

The energy stored inside the planet (in whatever the form) would mean a catastrophic potential of destroying said planet in a supernova like explosion.
When so much energy suddenly gets released, it would blow apart most of the planetary body and - if a planetary sized husk remains - that husk would be insanely hot. So hot it would glow bright like a star for some time while continously dimming again due to the energy radiated to space.

Energy does have mass. E=mc^2. It is established science that energy itself exerts a gravitational force.
– NeutronStarApr 6 '16 at 14:19

1

Energy does NOT have mass. It is EQUIVALENT to mass - as in it can be exchanged for mass and the amount can be calculated by Einstein's formula you cited, however any amount of pure energy has a mass of exactly 0 (examples for that are electro magnetic waves, gravitational waves etc. all have energy but no mass). Basically everything that doesn't have a Higgs Field interaction is massless.
– AdwaenythApr 6 '16 at 14:25

Considering they absorbed the full gravitational energy as well as all the currently available fusion energy (fusion would likely stop when you find a way to drain all energy from a star) they'd end up with something like less than 10^44J (the energy released by a supernova). If you put that through Einstein's equation, the mass added would be 10^28kg. That would be 2000 times the mass of earth... so they found a way to store the energy outside of normal physics or everything on the surface would be flattend to less than a cm in height.
– AdwaenythApr 7 '16 at 5:50